import 'dart:isolate';
import 'dart:ui';
import 'dart:async';
import 'dart:io';

import 'package:device_info_plus/device_info_plus.dart';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:flutter_downloader/flutter_downloader.dart';
import 'package:permission_handler/permission_handler.dart';

class DownPage extends StatefulWidget {
  @override
  _DownPageState createState() => _DownPageState();
}

class _DownPageState extends State<DownPage> {
  final _documents = [
    {
      'name': 'Learning Android Studio',
      'link':
      'http://barbra-coco.dyndns.org/student/learning_android_studio.pdf'
    },
    {
      'name': 'Android Programming Cookbook',
      'link':
      'http://enos.itcollege.ee/~jpoial/allalaadimised/reading/Android-Programming-Cookbook.pdf'
    },
    {
      'name': 'iOS Programming Guide',
      'link':
      'http://darwinlogic.com/uploads/education/iOS_Programming_Guide.pdf'
    },
    {
      'name': 'Objective-C Programming (Pre-Course Workbook',
      'link':
      'https://www.bignerdranch.com/documents/objective-c-prereading-assignment.pdf'
    },
  ];

  final _images = [
    {
      'name': 'Arches National Park',
      'link':
      'https://upload.wikimedia.org/wikipedia/commons/6/60/The_Organ_at_Arches_National_Park_Utah_Corrected.jpg'
    },
    {
      'name': 'Canyonlands National Park',
      'link':
      'https://upload.wikimedia.org/wikipedia/commons/7/78/Canyonlands_National_Park%E2%80%A6Needles_area_%286294480744%29.jpg'
    },
    {
      'name': 'Death Valley National Park',
      'link':
      'https://upload.wikimedia.org/wikipedia/commons/b/b2/Sand_Dunes_in_Death_Valley_National_Park.jpg'
    },
    {
      'name': 'Gates of the Arctic National Park and Preserve',
      'link':
      'https://upload.wikimedia.org/wikipedia/commons/e/e4/GatesofArctic.jpg'
    }
  ];

  final _videos = [
    {
      'name': 'Big Buck Bunny',
      'link':
      'http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4'
    },
    {
      'name': 'Elephant Dream',
      'link':
      'http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/ElephantsDream.mp4'
    }
  ];

  List<_TaskInfo>? _tasks;
  late List<_ItemHolder> _items;
  late bool _isLoading;
  late bool _permissionReady;
  late String _localPath;
  ReceivePort _port = ReceivePort();

  @override
  void initState() {
    super.initState();

    _bindBackgroundIsolate();

    FlutterDownloader.registerCallback(downloadCallback);

    _isLoading = true;
    _permissionReady = false;

    _prepare();
  }

  @override
  void dispose() {
    _unbindBackgroundIsolate();
    super.dispose();
  }

  void _bindBackgroundIsolate() {
    bool isSuccess = IsolateNameServer.registerPortWithName(
        _port.sendPort, 'downloader_send_port');
    if (!isSuccess) {
      _unbindBackgroundIsolate();
      _bindBackgroundIsolate();
      return;
    }
    _port.listen((dynamic data) {
      print('UI Isolate Callback: $data');

      String? id = data[0];
      DownloadTaskStatus? status = data[1];
      int? progress = data[2];

      if (_tasks != null && _tasks!.isNotEmpty) {
        final task = _tasks!.firstWhere((task) => task.taskId == id);
        setState(() {
          task.status = status;
          task.progress = progress;
        });
      }
    });
  }

  void _unbindBackgroundIsolate() {
    IsolateNameServer.removePortNameMapping('downloader_send_port');
  }

  static void downloadCallback(
      String id, DownloadTaskStatus status, int progress) {

      print(
          'Background Isolate Callback: task ($id) is in status ($status) and process ($progress)');

    final SendPort send =
    IsolateNameServer.lookupPortByName('downloader_send_port')!;
    send.send([id, status, progress]);
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('下载'),
      ),
      body: Builder(
          builder: (context) => _isLoading
              ? new Center(
            child: new CircularProgressIndicator(),
          )
              : _permissionReady
              ? _buildDownloadList()
              : _buildNoPermissionWarning()),
    );
  }

  Widget _buildDownloadList() => Container(
    child: ListView(
      padding: const EdgeInsets.symmetric(vertical: 16.0),
      children: _items
          .map((item) => item.task == null
          ? _buildListSection(item.name!)
          : DownloadItem(
        data: item,
        onItemClick: (task) {
          _openDownloadedFile(task).then((success) {
            if (!success) {
              Scaffold.of(context).showSnackBar(SnackBar(
                  content: Text('Cannot open this file')));
            }
          });
        },
        onActionClick: (task) {
          if (task.status == DownloadTaskStatus.undefined) {
            _requestDownload(task);
          } else if (task.status == DownloadTaskStatus.running) {
            _pauseDownload(task);
          } else if (task.status == DownloadTaskStatus.paused) {
            _resumeDownload(task);
          } else if (task.status == DownloadTaskStatus.complete) {
            _delete(task);
          } else if (task.status == DownloadTaskStatus.failed) {
            _retryDownload(task);
          }
        },
      ))
          .toList(),
    ),
  );

  Widget _buildListSection(String title) => Container(
    padding: const EdgeInsets.symmetric(horizontal: 16.0, vertical: 8.0),
    child: Text(
      title,
      style: TextStyle(
          fontWeight: FontWeight.bold, color: Colors.blue, fontSize: 18.0),
    ),
  );

  Widget _buildNoPermissionWarning() => Container(
    child: Center(
      child: Column(
        mainAxisSize: MainAxisSize.min,
        crossAxisAlignment: CrossAxisAlignment.center,
        children: [
          Padding(
            padding: const EdgeInsets.symmetric(horizontal: 24.0),
            child: Text(
              'Please grant accessing storage permission to continue -_-',
              textAlign: TextAlign.center,
              style: TextStyle(color: Colors.blueGrey, fontSize: 18.0),
            ),
          ),
          SizedBox(
            height: 32.0,
          ),
          FlatButton(
              onPressed: () {
                _retryRequestPermission();
              },
              child: Text(
                'Retry',
                style: TextStyle(
                    color: Colors.blue,
                    fontWeight: FontWeight.bold,
                    fontSize: 20.0),
              ))
        ],
      ),
    ),
  );

  Future<void> _retryRequestPermission() async {
    final hasGranted = await _checkPermission();

    if (hasGranted) {
      await _prepareSaveDir();
    }

    setState(() {
      _permissionReady = hasGranted;
    });
  }

  void _requestDownload(_TaskInfo task) async {
    task.taskId = await FlutterDownloader.enqueue(
      url: task.link!,
      headers: {"auth": "test_for_sql_encoding"},
      savedDir: _localPath,
      showNotification: true,
      openFileFromNotification: true,
      saveInPublicStorage: true,
    );
  }

  void _cancelDownload(_TaskInfo task) async {
    await FlutterDownloader.cancel(taskId: task.taskId!);
  }

  void _pauseDownload(_TaskInfo task) async {
    await FlutterDownloader.pause(taskId: task.taskId!);
  }

  void _resumeDownload(_TaskInfo task) async {
    String? newTaskId = await FlutterDownloader.resume(taskId: task.taskId!);
    task.taskId = newTaskId;
  }

  void _retryDownload(_TaskInfo task) async {
    String? newTaskId = await FlutterDownloader.retry(taskId: task.taskId!);
    task.taskId = newTaskId;
  }

  Future<bool> _openDownloadedFile(_TaskInfo? task) {
    if (task != null) {
      return FlutterDownloader.open(taskId: task.taskId!);
    } else {
      return Future.value(false);
    }
  }

  void _delete(_TaskInfo task) async {
    await FlutterDownloader.remove(
        taskId: task.taskId!, shouldDeleteContent: true);
    await _prepare();
    setState(() {});
  }

  Future<bool> _checkPermission() async {
    DeviceInfoPlugin deviceInfo = DeviceInfoPlugin();
    AndroidDeviceInfo androidInfo = await deviceInfo.androidInfo;
    if (Platform.isAndroid && (androidInfo.version.sdkInt??28) <= 28) {
      final status = await Permission.storage.status;
      if (status != PermissionStatus.granted) {
        final result = await Permission.storage.request();
        if (result == PermissionStatus.granted) {
          return true;
        }
      } else {
        return true;
      }
    } else {
      return true;
    }
    return false;
  }

  Future<Null> _prepare() async {
    final tasks = await FlutterDownloader.loadTasks();

    int count = 0;
    _tasks = [];
    _items = [];

    _tasks!.addAll(_documents.map((document) =>
        _TaskInfo(name: document['name'], link: document['link'])));

    _items.add(_ItemHolder(name: 'Documents'));
    for (int i = count; i < _tasks!.length; i++) {
      _items.add(_ItemHolder(name: _tasks![i].name, task: _tasks![i]));
      count++;
    }

    _tasks!.addAll(_images
        .map((image) => _TaskInfo(name: image['name'], link: image['link'])));

    _items.add(_ItemHolder(name: 'Images'));
    for (int i = count; i < _tasks!.length; i++) {
      _items.add(_ItemHolder(name: _tasks![i].name, task: _tasks![i]));
      count++;
    }

    _tasks!.addAll(_videos
        .map((video) => _TaskInfo(name: video['name'], link: video['link'])));

    _items.add(_ItemHolder(name: 'Videos'));
    for (int i = count; i < _tasks!.length; i++) {
      _items.add(_ItemHolder(name: _tasks![i].name, task: _tasks![i]));
      count++;
    }

    tasks!.forEach((task) {
      for (_TaskInfo info in _tasks!) {
        if (info.link == task.url) {
          info.taskId = task.taskId;
          info.status = task.status;
          info.progress = task.progress;
        }
      }
    });

    _permissionReady = await _checkPermission();

    if (_permissionReady) {
      await _prepareSaveDir();
    }

    setState(() {
      _isLoading = false;
    });
  }

  Future<void> _prepareSaveDir() async {
    _localPath = (await _findLocalPath())!;
    final savedDir = Directory(_localPath);
    bool hasExisted = await savedDir.exists();
    if (!hasExisted) {
      savedDir.create();
    }
  }

  Future<String?> _findLocalPath() async {
    var externalStorageDirPath;
    // if (Platform.isAndroid) {
    //   try {
    //     externalStorageDirPath = await getTemporaryDirectory();
    //   } catch (e) {
    //     final directory = await getExternalStorageDirectory();
    //     externalStorageDirPath = directory?.path;
    //   }
    // } else if (Platform.isIOS) {
      externalStorageDirPath =
          (await getApplicationDocumentsDirectory()).absolute.path;
    // }
    return externalStorageDirPath;
  }
}

class DownloadItem extends StatelessWidget {
  final _ItemHolder? data;
  final Function(_TaskInfo?)? onItemClick;
  final Function(_TaskInfo)? onActionClick;

  DownloadItem({this.data, this.onItemClick, this.onActionClick});

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.only(left: 16.0, right: 8.0),
      child: InkWell(
        onTap: data!.task!.status == DownloadTaskStatus.complete
            ? () {
          onItemClick!(data!.task);
        }
            : null,
        child: Stack(
          children: <Widget>[
            Container(
              width: double.infinity,
              height: 64.0,
              child: Row(
                crossAxisAlignment: CrossAxisAlignment.center,
                children: <Widget>[
                  Expanded(
                    child: Text(
                      data!.name!,
                      maxLines: 1,
                      softWrap: true,
                      overflow: TextOverflow.ellipsis,
                    ),
                  ),
                  Padding(
                    padding: const EdgeInsets.only(left: 8.0),
                    child: _buildActionForTask(data!.task!),
                  ),
                ],
              ),
            ),
            data!.task!.status == DownloadTaskStatus.running ||
                data!.task!.status == DownloadTaskStatus.paused
                ? Positioned(
              left: 0.0,
              right: 0.0,
              bottom: 0.0,
              child: LinearProgressIndicator(
                value: data!.task!.progress! / 100,
              ),
            )
                : Container()
          ].toList(),
        ),
      ),
    );
  }

  Widget? _buildActionForTask(_TaskInfo task) {
    if (task.status == DownloadTaskStatus.undefined) {
      return RawMaterialButton(
        onPressed: () {
          onActionClick!(task);
        },
        child: Icon(Icons.file_download),
        shape: CircleBorder(),
        constraints: BoxConstraints(minHeight: 32.0, minWidth: 32.0),
      );
    } else if (task.status == DownloadTaskStatus.running) {
      return RawMaterialButton(
        onPressed: () {
          onActionClick!(task);
        },
        child: Icon(
          Icons.pause,
          color: Colors.red,
        ),
        shape: CircleBorder(),
        constraints: BoxConstraints(minHeight: 32.0, minWidth: 32.0),
      );
    } else if (task.status == DownloadTaskStatus.paused) {
      return RawMaterialButton(
        onPressed: () {
          onActionClick!(task);
        },
        child: Icon(
          Icons.play_arrow,
          color: Colors.green,
        ),
        shape: CircleBorder(),
        constraints: BoxConstraints(minHeight: 32.0, minWidth: 32.0),
      );
    } else if (task.status == DownloadTaskStatus.complete) {
      return Row(
        mainAxisSize: MainAxisSize.min,
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          Text(
            'Ready',
            style: TextStyle(color: Colors.green),
          ),
          RawMaterialButton(
            onPressed: () {
              onActionClick!(task);
            },
            child: Icon(
              Icons.delete_forever,
              color: Colors.red,
            ),
            shape: CircleBorder(),
            constraints: BoxConstraints(minHeight: 32.0, minWidth: 32.0),
          )
        ],
      );
    } else if (task.status == DownloadTaskStatus.canceled) {
      return Text('Canceled', style: TextStyle(color: Colors.red));
    } else if (task.status == DownloadTaskStatus.failed) {
      return Row(
        mainAxisSize: MainAxisSize.min,
        mainAxisAlignment: MainAxisAlignment.end,
        children: [
          Text('Failed', style: TextStyle(color: Colors.red)),
          RawMaterialButton(
            onPressed: () {
              onActionClick!(task);
            },
            child: Icon(
              Icons.refresh,
              color: Colors.green,
            ),
            shape: CircleBorder(),
            constraints: BoxConstraints(minHeight: 32.0, minWidth: 32.0),
          )
        ],
      );
    } else if (task.status == DownloadTaskStatus.enqueued) {
      return Text('Pending', style: TextStyle(color: Colors.orange));
    } else {
      return null;
    }
  }
}

class _TaskInfo {
  final String? name;
  final String? link;

  String? taskId;
  int? progress = 0;
  DownloadTaskStatus? status = DownloadTaskStatus.undefined;

  _TaskInfo({this.name, this.link});
}

class _ItemHolder {
  final String? name;
  final _TaskInfo? task;

  _ItemHolder({this.name, this.task});
}
